我想在自定义控件中调用OnPaint事件。我创建了一个类和继承的控件来创建自定义控件，并希望在初始化对象时调用OnPaint或绘制事件。但是当我创建一个类时，不会触发paint事件。请看下面的代码。
internal class CallRectangle : Control
{
public CallRectangle()
{
this.Paint += CalloutRectangle_Paint;
}
void CalloutRectangle_Paint(object sender, PaintEventArgs e)
{
throw new NotImplementedException();
}
protected override void OnPaint(PaintEventArgs e)
{
}
}
// Create object to the custom control and call paint event using constructor
CallRectangle obj = new CallRectangle();
this.Controls.Add(obj);
任何人都让我知道如何调用paint事件。
谢谢， Bharathi。
答案 0 :(得分：1)
为您调用无效，更新或刷新无效。
这是一个可下载的Sample from Microsoft，其中包含如何直接从控件继承的分步指南，并构建绘制事件，因为继承自一个现有的控件（按钮让我们说）非常简单，因为它已经自我绘制了。
您将在上面的示例中看到，您需要根据控件的复杂性创建多个绘图事件（例如，包含需要绘制项目的列表框）。上面链接的示例代码：
/// <include file='DocumentationComments.xml' path='doc/members/member[@name="M:TwoLineListBox.OnPaint"]/*'/>
protected override void OnPaint(PaintEventArgs e)
{
base.OnPaint(e);
// draw on memory bitmap
CreateMemoryBitmap();
// TODO: Figure out how to avoid doing this on every paint
// calculate fields required to layout and draw list
RecalcItems(e.Graphics);
Graphics g = Graphics.FromImage(m_bmp);
// Draw the background and raise the PaintBackground event
OnPaintBackground(new ListPaintEventArgs(g));
// draw list
if (m_list != null)
DrawItems(g);
// Draw the frame around the list
Rectangle rc = new Rectangle(0, 0, this.Width - m_scrollBarWidth, this.Height - 1);
g.DrawRectangle(new Pen(Color.Black), rc);
// blit memory bitmap to screen
e.Graphics.DrawImage(m_bmp, 0, 0);
}
// This prevents the base class from doing OnPaintBackground.
// Since the OnPaint method paints the entire window there's no reason
// to let this go through. If we do it'll cause flashing.
/// <include file='DocumentationComments.xml' path='doc/members/member[@name="M:TwoLineListBox.OnPaintBackground"]/*'/>
protected override void OnPaintBackground(PaintEventArgs e)
{
}
// Called when it is time to draw the background. To take complete control of background
// drawing override this. To get called after the background is drawn by the base class
// register for the PaintBackground event.
/// <include file='DocumentationComments.xml' path='doc/members/member[@name="M:TwoLineListBox.OnPaintBackgroundII"]/*'/>
protected virtual void OnPaintBackground(ListPaintEventArgs e)
{
// Fill the background with the background colour
e.Graphics.Clear(this.BackColor);
if (PaintBackground != null)
PaintBackground(this, e);
}
// Called to draw a line item. To take complete control of drawing an item override this method.
// To let the base class draw the item first and then do your own additional work register for the
// PaintItem event.
/// <include file='DocumentationComments.xml' path='doc/members/member[@name="M:TwoLineListBox.OnPaintItem"]/*'/>
protected virtual void OnPaintItem(ListPaintEventArgs e)
{
Graphics g = e.Graphics;
Rectangle destRect = new Rectangle(); // Destination for the item image, if any
Rectangle srcRect = new Rectangle(); // Source region of the image to draw
Rectangle textRect = new Rectangle(); // Destination for the text
int lineIndent = 0; // How far the text is moved in from the left margin before drawing
Image imageToDraw = null;
string line1Text;
string line2Text;
// On the null case skip everything and just draw the separator line
if (e.Item == null)
goto DrawSeparator;
line1Text = GetStringProperty(e.Item, this.m_line1Property);
if (line1Text == null)
line1Text = e.Item.ToString();
line2Text = GetStringProperty(e.Item, this.m_line2Property);
if (line2Text == null)
line2Text = e.Item.ToString();
// Figure out if we're drawing an image per item from the object, or one for
// everything
imageToDraw = GetImageProperty(e.Item, this.m_itemImageProperty);
if (imageToDraw == null)
imageToDraw = m_itemImage;
// Calculate the position of the item image, if we have one, and the line indents
if (imageToDraw != null)
{
srcRect.X = 0;
srcRect.Y = 0;
srcRect.Width = imageToDraw.Width;
srcRect.Height = imageToDraw.Height;
// int vertPos = (m_itemHeight - m_itemImage.Height) / 2;
destRect.X = e.ClipRectangle.X + IMAGE_PADDING_X;
destRect.Y = e.ClipRectangle.Y + IMAGE_PADDING_Y;
// destRect.Y = (vertPos < 0) ? 0 : vertPos; // Center the image vertically in the line height. Handle the image being larger than the item height
// Account for an image that is taller than the item height
destRect.Height = (imageToDraw.Height > m_itemHeight - IMAGE_PADDING_Y) ? m_itemHeight - (IMAGE_PADDING_Y * 2) : imageToDraw.Height;
destRect.Width = destRect.Height;
// Set the text indent based on the image
lineIndent = IMAGE_PADDING_X + imageToDraw.Width + TEXT_PADDING_X; // Two pixels for the left indent of the image
}
else
{
// Set the text indent without using the image
lineIndent = TEXT_PADDING_X;
}
// Calculate the text rectangle
textRect.X = e.ClipRectangle.X + lineIndent;
textRect.Width = e.ClipRectangle.Width - TEXT_PADDING_X - textRect.X; // Allows for padding on the right edge too
textRect.Y = e.ClipRectangle.Y + 2;
textRect.Height = this.m_textHeightLine1;
// From here on we actually draw things. First the selected background, if necessary
if (e.Selected)
g.FillRectangle(m_brushSelBack, e.ClipRectangle);
// Draw the icon, if we have one
if (imageToDraw != null)
{
if (m_useTransparent)
g.DrawImage(imageToDraw, destRect, srcRect.Y, srcRect.Y, srcRect.Height, srcRect.Height,
GraphicsUnit.Pixel, m_imageAttributes);
else
g.DrawImage(imageToDraw, destRect, srcRect, GraphicsUnit.Pixel);
}
// Draw the text in a bounding rect to force it to truncate if too long
g.DrawString(line1Text, m_fontLine1, e.Selected ? m_brushSelText : m_brushText, textRect);
// Draw the second line
textRect.Y += m_textHeightLine1 + 3;
textRect.Height = this.m_textHeightLine2;
g.DrawString(line2Text, m_fontLine2, e.Selected ? m_brushSelText : m_brushText, textRect);
DrawSeparator:
// Draw the separator line
g.DrawLine(m_penSep, e.ClipRectangle.X, e.ClipRectangle.Y + e.ClipRectangle.Height,
e.ClipRectangle.X + e.ClipRectangle.Width, e.ClipRectangle.Y + e.ClipRectangle.Height);
// Let other people know it's time for them to draw
if (PaintItem != null)
PaintItem(this, e);
}
// Draw all the items.
private void DrawItems(Graphics g)
{
ListPaintEventArgs ListPaintEventArgs = new ListPaintEventArgs(g);
// Calculate our actual drawing area, accounting for the scroll bar
Rectangle rc = new Rectangle(0, 0, this.Width - m_scrollBarWidth, this.Height - 1);
// draw items that are visible
int curItem = 0;
for (int i = 0; (i < m_visibleCount); i++)
{
curItem = i + m_topItem;
if (curItem < m_list.Count)
{
// Calculate the drawing area for the item
ListPaintEventArgs.ClipRectangle = new Rectangle(rc.X,
rc.Y + (i * m_itemHeight),
rc.Width,
this.m_itemHeight);
// Get the item we'll be drawing with and whether it is selected
ListPaintEventArgs.Item = m_list[curItem];
ListPaintEventArgs.Selected = (m_selItem == curItem);
// Draw the item
OnPaintItem(ListPaintEventArgs);
}
}
}
// Recalculates the heights and visible counts for assorted items
// in the listbox.
// TODO: Get rid of this method by moving the rest of the items into the assorted
// properties.
private void RecalcItems(Graphics g)
{
// The text heights for a single line of text is the height of the font.
m_textHeightLine1 = g.MeasureString("W", this.m_fontLine1).ToSize().Height;
m_textHeightLine2 = g.MeasureString("W", this.m_fontLine2).ToSize().Height;
// The height for an individual item is two lines plus some padding
m_itemHeight = m_textHeightLine1 + m_textHeightLine2 + 5;
m_visibleCount = this.Height / m_itemHeight;
// Set the top item to draw to the current scroll position
m_topItem = m_scrollValue;
}
// Creates all the objects we need for drawing
private void CreateGdiObjects()
{
m_brushText = new SolidBrush(this.ForeColor);
m_brushSelText = new SolidBrush(this.m_selForeColor);
m_brushSelBack = new SolidBrush(this.m_selBackColor);
m_penSep = new Pen(this.m_separatorColor);
m_imageAttributes = new ImageAttributes();
}
// Creates a bitmap in memory to do our drawing. We'll draw on this first
// and then splat it to the screen.
private void CreateMemoryBitmap()
{
// Only create if don't have one and the size hasn't changed
if (m_bmp == null || m_bmp.Width != this.Width || m_bmp.Height != this.Height)
{
m_bmp = new Bitmap(this.Width - m_scrollBarWidth, this.Height);
// TODO: Figure out why this is here.
m_scrollBar.Left = this.Width - m_scrollBarWidth;
m_scrollBar.Top = 0;
m_scrollBar.Width = m_scrollBarWidth;
m_scrollBar.Height = this.Height;
}
}
我希望这有帮助